The inventive concept relates to touch panels, display devices and touch screen systems. More particularly, the inventive concept relates to methods and apparatuses improving the sensitivity and discrimination performance of the touch panels.
Portable electronic devices have become smaller and thinner to meet user demand. Touch screens allowing the omission of mechanical buttons have improved the look and feel of modern electronic devices and enabled appealing design that are widely used in general asynchronous transfer mode (ATM) devices, televisions (TVs), and general home appliances as well as small-sized portable devices. Cell phones, portable multimedia players (PMPs), personal digital assistants (PDAs), e-books, are ready examples of small-sized portable electronic devices that benefit from the incorporation of touch screens. In order to further reduce the physical size and operating complexity of such devices various approaches to the integration of user input interfaces (e.g., input buttons) with a display screen have been explored. As part of this ongoing process of interface-to-screen integration, touch detection (or perception) technology has been the subject of much research and development. “Touch perception” is a broad field of technology that seeks to intelligently and accurately perceive a touch input to a user interface surface, such as a display screen.
Generally, a “touch screen” is a type of visual display which has been further enabled to serve as a user interface. That is a touch screen is an input device that constitutes an interface between an information communication device using a displays and a user. The user directly contacts the touch screen with a “touch mechanism” such as a finger, pen, stylus, or the like in order to input information (e.g., data and/or commands) to the information communication device. Certain types of panel display devices, including liquid crystal display (LCD) devices, field emission display (FED) devices, organic light-emitting diode (OLED) devices, plasma display (PDP) devices, and the like, are commonly used as a touch screen.
Flat panel display devices generally include a plurality of pixels arranged in a row-column matrix to display electronically and/or optically derived images. For example, LCD devices may include a plurality of scan lines that communicate gate signals and a plurality of data lines that communicate gray scale data. Individual pixels are formed at points where a scan line and a data line cross. Each pixel may include a transistor/capacitor combination, or simply a capacitor.
Touch screens use various methods to detect user touch inputs, including resistive overlay, capacitive overlay, surface acoustic wave, infrared, surface elastic wave, inductive, and the like.
In a touch screen using the resistive overlay method, a resistive material is coated on a glass or transparent plastic plate, and a polyester film is covered thereon, and insulating rods are installed at regular intervals so that two sides of the polyester film do not contact each other. In this case, resistance and voltage are varied. However, the position of the user's hand as it contacts the touch screen may erroneously be perceived as an input, or may alter the degree of voltage variation for an intended user input. Touch screens using the resistive overlay method are superior in their performance characteristics when cursive script is input by a user, but they are also characterized by low transmittance, low durability, and problems associated with the detection of multi-contact points.
In a touch screen using the surface acoustic wave method, a transmitter emitting sound waves and a reflector reflecting the sound waves at regular intervals are attached to a one corner of glass display plane. A receiver is attached to the opposite corner of the glass. When the glass is then touched the transmission of the sound waves is interrupted. By determining (or calculating) the point of interruption, the location of the touch input may be perceived.
In a touch screen using the infrared method, the directivity of applied infrared light may be used to perceive the location of a touch input. A matrix may be formed from an arrangement of infrared light-emitting diodes (LEDs) as a spontaneous emission device and a phototransistor as a light receiving device. As with the sound waves in the surface acoustic wave method, a detected interception in the transmission of the infrared light caused by a touch input may be used to determine the location of the touch input.
Contemporary, portable electronic devices mainly use the resistive overlay method which is low cost and is compatible with various input mechanisms. However, as research into user interfaces enabling multiple, simultaneous touch inputs (hereafter, “multi-touch”) has continued, touch screens using the capacitive overlay method have become prominent dues to there ability to effectively interpret multi-touch.